1. Field of the Invention
This invention relates to an improved package, especially a so-called skin-type package.
2. Prior Art
Many different package structures have been provided with a variety of convenient opening features. For example, tear strings have been used with mailing tubes and other tubular containers and cartons for a great many years and tear strips on gum wrappers and cigarette packages are well known. With the more recent advent of packages utilizing plastic film, the effectiveness of tear strings has been impaired because of the difficulty with which some of the plastic films are torn. At the same time, the high tear strength of these films increases the need for an opening device. In addition, such films are typically tightly wrapped about, drawn over or shrunk about a product, making it difficult to grasp the film to tear it open.
Tear strips or the like have been proposed for certain types of packages made of plastic film, such as plastic bags and certain shrink-type packages, but have heretofore not been satisfactory for skin-type packages of the type where a product is supported on a card or panel by a relatively strong plastic film that is securely adhered thereto. This is understandable when it is realized that, for the tear string to be conveniently included and to function most effectively with such a package, it must be applied across the article itself, along with the film, so that manipulation of the string during placement is minimized and the string is positioned to sever the film in a location that readily facilitates direct removal of the article. On the other hand, such a location proves to be unsatisfactory with typical tear strings. This is because the tear string does not initially follow the contour of the article, but is merely draped across the article and panel, there is normally insufficient slack in the string to promote conformance to the article, and the film is softened by heat to conform to the product. As a result, the film will be initially suspended by the string, like a tent, away from side portions of the article and will then form around the string and be drawn together beneath the string span. When this happens, the string will not open the package satisfactorily, because the film is sealed beneath the string at the sides of the article. A further problem experienced by the applicant in initial attempts to develop a tear string for a skin-type package is that, except for the thinnest films, it is extremely difficult to tear plastic film with a string. With the heavier films, such as 10 mil (0.010 inch thick) polyethylene, it is extremely difficult and some times impossible to begin the tear by gripping a string with the fingers and pulling. This is especially true if the edge of the film is folded back upon itself to form a double thickness, as may be necessary in order to expose one end of the tear string.
In the forming of skin type packages, both the film that covers the product and a thermoplastic adhesive on the panel are heated to facilitate conformance of the film to the product being packaged and adherence of the film to the panel. It has generally been difficult to soften the film and also the adhesive coating on the panel without overheating either the panel or the film or both in the process.